Abstract: Surfaces repair is one of the most useful techniques in surface modeling.That is referred to how a model represented by many trimmed surfaces is transferred to a watertight model.The method of dispersing boundary curves and repairing surfaces is used in many papers.But the error of dispersing is hard to be controlled.An algorithm of trimmed surfaces repair is presented.Neighbor surfaces information is constructed by the geometric data of surfaces to be repaired.Neighbor boundary curves information is found by the neighbor surfaces information.Then matched parameters of matched curves are obtained by neighbor boundary curves information.Topological information of surfaces is constructed.Finally,surfaces are repaired by topological information of trimmed surfaces.Samples are given to prove the algorithm,which show that the quality of surfaces repair is good.